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TPS23881: Value of channel 1/2/3/4 discovery registers(0c-0f) not getting updated before sending PWON command.

Part Number: TPS23881

Hi,

I have to implement a new feature which is to set power budget limit on a port based on class.We are allowing the user to specify the class also alongwith poe enable command on a port so that if a new PD connected to that port,first we can check what is the class of the PD using 0c-0f registers and compare the class with what user has configured,if it turns out to be same or lower class than what the user has configured,we would turn on the PD otherwise throw some error logs.

e.g poe enable <class>.

As part of this poe enable command,I was doing 2 things as part of register settings:
1.Enabling detection enable register(0x14).
2.Sending PWON command (0x19).

Now as per the requirement,need to add a third thing between the two:
1.Enabling detection enable register(0x14).
2.Check 0c-0f registers and compare the class with class configured.----------------This check is always giving me 0x0 even after adding 5 sec delay after step 1.
3..Sending PWON command (0x19).

After step3 when I checking 0c-0f regsiters,they are properly giving me class of the PD connected.

Can sombody help me with this,can my requirement be fulfilled by doing some regsiter settings?

Hoping an early reply.

Thanks & Regards

Ayush Raj

  • Hi Ayush,

    Thanks for reaching out.

    Our PSE expert is traveling. The reply may be delayed.

    Best regards,

    Diang

  • Hi Ayush,

    Thanks for your patience as I have been out of office traveling. 

    Can you confirm the following:

    What operating mode are you in (Register 0x12)?

    What is your port power allocation (Register 0x29) prior to turning on the ports?

    Please confirm your load SRAM upon bootup.

    What is the value being written to Register 0x14? Are you enabling classification as well as detection? If you are in manual mode your will need to set this every single time you wish to do a detection and classification cycle. In semi-auto mode this will be done automatically onces these bits are set. 

    Regards,

    Brandon